The present invention relates to resealable closures and more specifically to closures that comprise a spout and overcap that seal together as a unit that can be welded by the use of an induction heat sealing double-sided foil to a container.
This type of resealable closure was first described by Spreckelsen McGeough Ltd in GB-A-2 337 740. That patent specification disclosed for the first time the idea of sealing a neck and cap assembly (referred to herein as a spout and overcap) to the mouth or neck of a polyolefin bottle, preferably by means of a foil (preferably aluminium) coated on both sides with a plastics material that will weld or adhere to the adjacent component. This type of foil with plastics coatings on each surface is described herein as a double-sided foil. In this structure the welding of the foil to the container mouth creates the primary ex-factory seal. This type of resealable closure is generally referred to herein as the BAP® closure technology and GB-A-2 337 740 describes some exemplary embodiments of this technology.
Such resealable closures are particularly advantageous for use in large-scale dairy bottling, but have also been adapted for use with PET and other gas-tight containers as well as in carton fitments and closures for cans.
EP-A-13 65 957 (Mavin et al) describes a variation of the BAP® closure technology in which a spout and overcap are sealed to a bottle neck by a sealing medium which is received in a space defined between co-operating profiles of the closure and neck of the bottle. Mavin teaches that this space must not communicate with the opening at the neck of the bottle. Mavin suggests that the sealing medium might be an annular double-sided foil in the same manner as the BAP® closure technology.
There is also considerable investment in the packaging industry in polyolefin bottles with threaded necks. These existing bottles are usually provided with a primary seal by means of a relatively thick, pealable conduction or induction foil that seals over the mouth of the bottle neck. This is a one-sided foil. A secondary seal is attempted by means of a screw-threaded injection moulded overcap that engages with a threaded neck of the bottle. This secondary seal is notoriously leaky and leaves consumers much dissatisfied. The presence of the foil also means that the initial removal of the overcap sometimes requires considerable torque due to inadvertent undesirable adhesion between foil and overcap.
There are circumstances where a bottling plant that does not have an exclusive supplier of bottles must use an existing neck profile and cannot take advantage of the possibility of the additional bottle light weighting that is available through the BAP® closure technology. While the BAP® closure can be used with such a mouth structure, the cap and spout would need to be reduced in size in order to fit within the existing closure envelope and this necessity gives rise to certain technical problems as discussed below that would not otherwise exist.
Mavin has also appreciated this need to maintain the cap silhouette the same as an existing industry standard and describes a solution in GB-A-2 399 814, which has a priority date of 26 Mar. 2003 prior to the priority date of this application but which was not published until 29 Sep. 2004 after the priority date of this application.